Maximum Value of Voltage Drop IEC 60364-5-52

The voltage drop between the origin of an installation and any load point should not be greater than the values in Table G.52.1, expressed with respect to the value of the nominal voltage of the installation.

Table G.52.1 – Voltage Drop

Type of Installation	Lighting (%)	Other Uses (%)
A – Low voltage installations supplied directly from a public low voltage distribution system	3	5
B – Low voltage installations supplied from private LV supply	6	8

- As far as possible, it is recommended that voltage drop within the final circuits does not exceed those indicated in installation Type A.
- When the main wiring systems of the installations are longer than 100 m, these voltage drops may be increased by 0.005% per meter of wiring system beyond 100 m, without this supplement being greater than 0.5%.
- Voltage drop is determined from the demand by the current-using equipment, applying diversity factors where applicable, from the values of the design current of the circuits.

NOTE 1: A greater voltage drop may be accepted
- For motor starting periods.
- For other equipment with high inrush current.

Provided that in both cases, it is ensured that the voltage variations remain within the limits specified in the relevant equipment standard.

NOTE 2: The following temporary conditions are excluded
- Voltage transients.
- Voltage variation due to abnormal operation.

Voltage Drop Calculation Formula
u = b * ((P1 * L * cos(φ) + λ * L * sin(φ)) / S) * I_B

Where:
- u = Voltage drop (in volts).
- b = Coefficient, 1 for three-phase circuits, 2 for single-phase circuits.
- P₁ = Resistivity of conductors in normal service, 1.25 times the resistivity at 20°C:
  - 0.0225 Ω mm²/m for copper.
  - 0.036 Ω mm²/m for aluminum.
- L = Straight length of the wiring system (in meters).
- S = Cross-sectional area of conductors (in mm²).
- cos φ = Power factor (default 0.8, if not specified).
- λ = Reactance per unit length of conductors, 0.08 mΩ/m in absence of other data.
- I_B = Design current (in amps).

The voltage drop percentage can be calculated as:
Δu = 100 * (u / U0)
where:
- U₀ = Voltage between line and neutral (in volts).

NOTE 4:
- In extra-low voltage circuits, it is not necessary to fulfill the voltage drop limits of Table G.1 for uses other than lighting (e.g., bell, control, door opening), provided that a check ensures that the equipment is operating correctly.

IEC 60364-6: Low voltage electrical installations – Part 6: Verification